Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 824990 | Metric tons | NA |
| 2004 | 1001053 | Metric tons | 21.34% |
| 2005 | 1149717 | Metric tons | 14.85% |
| 2006 | 1067684 | Metric tons | -7.14% |
| 2007 | 684668 | Metric tons | -35.87% |
| 2008 | 678000 | Metric tons | -0.97% |
